"On y mange bien, en qualité comme en quantité."
I thought on y mange bien meant 'we eat well', or 'let's eat well', but the correction says: 'We eat well there' where did the THERE came from?
The "y" refers to a place spoken of before in a conversation. For example, in the sentence, "j'aime ce restaurant, on y mange bien.", the "y" refers to "ce restaurant".